1. Field of the Invention
The present invention relates to an image encoding method, an image encoding circuit, an image encoding apparatus, and an optical disk for using an image signal that is digital band-compressed in a system in which errors may occur.
2. Description of the Related Art
In recent years, efforts to standardize moving picture coding methods as a standard for storage media such as CD-ROMs have been made by MPEG (Moving Picture Expert Group) of ISO/IEC SC29/WG11. In general, storing image data requires a huge amount of memory. Accordingly, techniques for efficiently compressing images to be stored in a storage medium are regarded as extremely important. An image coding method proposed by MPEG utilizes a DCT (Discreet Cosine Transform) method so as to reduce the redundancy of images in the spatial axis directions, and utilizes a predictive coding method so as to reduce the redundancy of the images in the time axis direction. The predictive coding takes advantage of the fact that there is a similarity between an identified image and its preceding images and succeeding images in successive moving pictures. Specifically, the predictive coding codes the difference between the image data to be coded and the preceding/succeeding image data, whereby the amount of data to be coded is greatly reduced.
According to the predictive coding method, given image data is used in the coding of other image data. As a result, an error that has occurred in the given image data is inevitably propagated to the image data to be predicted from the given image data. As the propagation range of the error increases, the process for correcting the error for reconstructing the image data becomes more complicated.